[PATCH 5.6 67/73] drm/i915/selftests: Fix i915_address_space refcnt leak

[Greg Kroah-Hartman]

From: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>

commit 5d5e100a20348c336e56df604b353b978f8adbb9 upstream.

igt_ppgtt_pin_update() invokes i915_gem_context_get_vm_rcu(), which
returns a reference of the i915_address_space object to "vm" with
increased refcount.

When igt_ppgtt_pin_update() returns, "vm" becomes invalid, so the
refcount should be decreased to keep refcount balanced.

The reference counting issue happens in two exception handling paths of
igt_ppgtt_pin_update(). When i915_gem_object_create_internal() returns
IS_ERR, the refcnt increased by i915_gem_context_get_vm_rcu() is not
decreased, causing a refcnt leak.

Fix this issue by jumping to "out_vm" label when
i915_gem_object_create_internal() returns IS_ERR.

Fixes: a4e7ccdac38e ("drm/i915: Move context management under GEM")
Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/1587361342-83494-1-git-send-email-xiyuyang19@xxxxxxxxxxxx
(cherry picked from commit e07c7606a00c4361bad72ff4e72ed0dfbefa23b0)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/i915/gem/selftests/huge_pages.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
+++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
@@ -1578,8 +1578,10 @@ static int igt_ppgtt_pin_update(void *ar
 		unsigned int page_size = BIT(first);
 
 		obj = i915_gem_object_create_internal(dev_priv, page_size);
-		if (IS_ERR(obj))
-			return PTR_ERR(obj);
+		if (IS_ERR(obj)) {
+			err = PTR_ERR(obj);
+			goto out_vm;
+		}
 
 		vma = i915_vma_instance(obj, vm, NULL);
 		if (IS_ERR(vma)) {
@@ -1632,8 +1634,10 @@ static int igt_ppgtt_pin_update(void *ar
 	}
 
 	obj = i915_gem_object_create_internal(dev_priv, PAGE_SIZE);
-	if (IS_ERR(obj))
-		return PTR_ERR(obj);
+	if (IS_ERR(obj)) {
+		err = PTR_ERR(obj);
+		goto out_vm;
+	}
 
 	vma = i915_vma_instance(obj, vm, NULL);
 	if (IS_ERR(vma)) {